Teardown: LED light shrinks size, cost with non-isolated driver

LED bulb prices are dropping. A year ago you could expect to pay $50 for a Philips dimmable 60W-replacement LED bulb, while today you can go to Best Buy and purchase its house brand 8W, 800 lumens Insignia 60W-replacement bulbfor just $17. What has changed in LED bulb design to allow this price drop? Tearing apart the bulb gives us a look into some design trends in LED lighting, such as how the LEDs are placed within the bulb and what driver architecture is used.

The Insignia bulb has a shape similar to the familiar incandescent light, with the addition of three metal heat sink fins, and a plastic bulb instead of glass (Figure 1).

Figure 1

Dimming is an important bulb characteristic for the US market. I used a Lutron Maestro dimming switch, with a programmable dimming control, and did a side-by-side comparison with an incandescent bulb. The Insignia dimmed consistently and smoothly, with a dimming profile similar to the incandescent bulb. You can watch a video of the dimming test here.

The next step was to look inside the bulb and see how the LEDs are mounted. Figure 2 shows the plastic bulb cover removed with a Dremmel tool, exposing the six Cree white LEDs that illuminate the bulb's light mixing chamber that allow an even glow with no pixelation. The metal fins that the LEDs are mounted on serve to both elevate the LEDs and serve as heat sinks.

Figure 2

At the bottom of the mixing chamber is a paper-thin aluminum reflector that helps reflect the light up and out of the bulb.

All of the electronics for this bulb lie beneath the mirror in the base of the bulb, in a separate and encapsulated compartment (More detailed photos are here).

Removing the rubbery potting compound shows that the electronics are mounted on two separate pc boards that nestle together. Figure 3 shows the two pc boards separated and next to the bulb's base.

Filament bulb: 2% of energy emitted as light, 88% as infrared, 10% as conducted heat. Filament at 2600°C, glass at ~100°C (regular bulb) to ~300°C (halogen). Bulb operates by being hot, so heat doesn't worry it. (It can melt lamp shade though.)
LED: ~20% of energy emitted as light, ~80% conducted heat. LED is very small, doesn't like being much over 100°C, so needs careful design to get heat away.
LED lighting can be cooler, safer and more efficient. (Some poor designs are not!)

I'm guessing those power supplies may burn out due to power supply spikes before those well regulated LEDs do. Or the failure of the supply is what will burn out the LEDs. Who knows? We might need replaceable power supply units for our 100 year LEDs!

It would be interesting to know an estimated cost of the electronics and if it would be possible to put all the electronics in one package (i.e. the base) that is separate from the actual LEDs and come up with something that could long-term keep the cost of replacement devices down when the LEDs finally burn out. That is, make the LED and/or Light producing part of the design replaceable, but the base resusable. It would probably require a more stable design that is not going to need to change over time so the electronics could be assured of being reusable. Lighting is one of the bigger reoccuring costs that people know are going to happen. Any way in which costs can be significantly reduced ,over the lifetime, would be a big help.

I can't help always returning to the irony of LED bulbs;
Q why are they more efficient?
A because they generate much more light and much less heat.
Q what is that huge ugly metal bit?
A A heat sink. because it neets to get rid of so much heat.
??

Wow. It takes a lot more eletronics than I would have expected, to drive these LEDs. One obvious problem is that they don't use 120 AC or 170 DC, and another must be that you need a current source to obtain predictable light output from individual LEDs.
Also, a lot of filtering going on there, with chokes and caps all over the place. Hopefully, this will prevent any significant amount of RF racket from being emitted.